How-to do to make some titles (« Introduction », « Conclusion », « Resume ») appear in the table without the page number?

You need to create a specific style for these headers, then affect to this style a level in the table of contents which will be set depending on your needs:

create a new style, for example Header1bis, based on Header 1;

set the style to the "Introduction", "Conclusion" and "Résumé" header;

right click the table of contents and select Edit index/table;

under the Index tab, check Additional styles and click the corresponding icon (…);

in the Additional style window that opens, select the new style Header1bis;

set the required level for the table of contents using the >> and << buttons: choose a level that is not used, for example 10;

press OK;

under the Entries tab, select the level that you previously set (10);

delete the unneeded elements in the Structure rule, click once on them then press the Suppr key;

under the Styles tab, select the predefined level (10) and set the level 1 paragraph style to it (Table of contents level 1) so the layout is the same for this two levels in the table of contents ;

press OK.

Note : the disadvantage of this solution is that it loses the actual hierarchy of the introduction and conclusion, and that even if there is no visible change in the document produced, this is reflected in the Navigator, especially when moving the chapters.

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